Valve manufacturers have supplied full port swing check valves for many years. These valves are invariably offered with cast bodies. The asserted advantages of cast bodies have been assumed, and are believed, to far outweigh any disadvantage.
The advantages of casting that dominate the thinking of the valve manufacturers are: (1) Casting makes possible designing essentially two piece bodies having complex, asymmetrical, detailed shapes. (2) Casting offers great versatility in alloy selection. (3) The tooling cost for casting is typically low. (4) Proper heat treating of casting reduces two conceivable disadvantages, brittleness and inflexibility.
The thinking in the industry has evolved to the point where a conviction exists that cast bodies are the only economically feasible and commercially viable alternative for swing check valves. The established valve manufacturers do not offer a forged body full port swing check valve and will not bid such a valve. Even if specified for a job, present valve manufacturers stubbornly quote a cast body valve.
In response to this unfilled need, the present inventor has invented a novel valve, e.g., a forged steel full port swing check valve. Forged steel has advantages of its own. Importantly, forged steel is less likely than cast steel to contain flaws. Flaws mean defects that might result in a leak. In particular, a forged steel body does not require welding for finishing the body to remove sand spots and slag, and a forged steel body does not require heat to remove excess metal from runners, gates, and risers. Both welding and the application of heat to a cast body can lead to structural weaknesses. To the contrary of casting, the forging process itself, the working of the metal, is believed to increase the flexibility of the steel and to align the granularity between the molecules, thereby enhancing the strength of the work piece. Experience shows that defect testing of cast valve bodies leads to the rejection of five to ten percent of the units. Similar reject testing of forged steel valve bodies results in a typical rejection of less than a half a percent. Therefore, because of enhanced environmental concerns associated with the operation of chemical and petrochemical plants and the transportation and storage of toxic fluids, a forged body full port swing check valve could have significant advantages.
Forged steel's major disadvantage is the inability to be formed into complex shapes. Forged body designs are limited to those that have simple shapes. Historically, a full port swing check valve does not exhibit a "simple shape". A "forged steel" full port swing check valve thus would have to overcome a major design obstacle, namely, being able to be "forged" in the standard two pieces.